The invention relates to a temperature measurement tube, intended for uses in refractory materials melted at very high temperatures.
Such a tube must resist the temperatures reached, and also the often very high corrosion which is observed in certain glasses, within the molten material as well as in the atmosphere that emanates therefrom. Crucibles containing the molten material are often cooled in order to spare them from these difficult conditions by forming a crust of solidified matter on the wall thereof, which is cooler and less corrosive than the molten material, but which prevents the temperature from being taken at the wall of the crucible. Use is therefore made of sufficiently long measurement tubes that are immersed in the bath of molten material and which contain a temperature measurement sensor.
Such tubes must themselves be able to resist the temperature reached and corrosion. It is possible to construct them with a hollow shaft wherein the cooling water flows, in such a way as to spare them, as with the crucible, from direct contact with the molten material. The cooling however cannot be extended until the end of the tube, where the measurement sensor is located, in order to not render the latter impossible. GB-1-120-547-A discloses such a measurement tube of high temperatures comprising a solid end-fitting fixed by threading to the end of the cooled shaft. A measurement thermocouple extends in a through-bore established in the heart of the end-fitting. An intermediary temperature between the temperature reached by the cooling water and the outside temperature to be measured is present in the end-fitting, which makes it possible to take measurements of the outside temperature after a suitable correction. The end-fitting however remains subjected to the corrosion, since all of the known materials that have the rigidity required to construct a long tube are sensitive to the excess.